Precision and accuracy testing of FMCW ladar-based length metrology

Area of Science:

• Metrology
• Optical Engineering
• Spectroscopy

Background:

• Accurate calibration and traceability of frequency modulated continuous wave (FMCW) ladar sources are crucial for precision length and volume measurements.
• Existing calibration methods may not provide the required uncertainty for advanced metrology applications.

Purpose of the Study:

• To establish a robust calibration method for FMCW ladar length measurement systems.
• To achieve and validate high-accuracy measurements in the parts per million (ppm) uncertainty range.

Main Methods:

• Utilized molecular spectroscopy of hydrogen cyanide (HCN) in the C-band and carbon monoxide (CO) in the L-band as frequency references.
• Calibrated the chirp rate of FMCW ladar sources using these molecular spectral lines.
• Developed a displacement measurement interferometer for comparative analysis.

Main Results:

• Achieved an estimated uncertainty of a few ppm for the FMCW ladar system by propagating uncertainties from molecular calibrations and measurement errors.
• Interferometer comparisons demonstrated agreement within <10 ppm with the calibrated FMCW system.
• The observed agreement was consistent with the combined estimated uncertainties of both measurement systems.

Conclusions:

• Molecular spectroscopy provides an effective method for calibrating FMCW ladar systems for high-accuracy metrology.
• The developed calibration technique meets the stringent uncertainty requirements for length and volume measurements.
• This approach enhances the traceability and reliability of FMCW ladar in precision engineering applications.